As used in this article:

1. (a) “License” means a valid and current license issued by the Commissioner of Labor in accordance with the provisions of this article.
2. (b) “Journeyman plumber” means a person qualified by passage of a journeyman plumber written examination with a score of at least 70 percent and who is competent to instruct and supervise the work of a plumber in training.
3. (c) “Master plumber” means a person who has passed a master plumber written examination with a score of at least 70 percent and who is competent to design plumbing systems, and to instruct and supervise the plumbing work of journeyman plumbers, and plumbers in training: Provided, That the master plumber written examination may not be taken until one year after passage of the journeyman plumber examination.
4. (d) “Plumber in training” means a person who has not passed the journeyman plumber examination: Provided, That the fee for plumbers in training may not be higher than $25.00.
5. (e) “Plumbing” means the practice, materials, and fixtures utilized within a building in the installation, extension, and alteration of all piping, fixtures, water treatment devices, plumbing appliances, and appurtenances, in connection with sanitary drainage or storm drainage facilities; the plumbing venting systems; medical gas systems; fuel oil and gas piping for residential, commercial, and institutional facilities; backflow preventers; and public or private water supply systems, as defined by the state building code.
6. (f) “Single family dwelling” means a building which is occupied as, or designed or intended for occupancy as, a single residence for one or more persons.